Print impression control for specially configured type elements



March 14, 1967 Dow 3,308,749

A. A. PRINT IMPRESSION CONTROL FOR SPECIALLY CONFIGURED TYPE ELEMENTS Filed May 24, 1965 l 2 Sheets-Sheet l llVl/E/VTO/q ALBERT A. DOWD ATTORNEY March 14, 1967 Filed May 24, 1965 A. A. DOWD PRINT IMPRESSION CONTROL FOR SPECIALLY CONFIGURED TYPE ELEMENTS 2 Sheets-Sheet 2 United States Eatent O Filed May 24, 1965, Ser. No. 458,336 14 Claims. (Cl. 101-93) This invention relates generally to printers and in particular to print impression control for an impact printer apparatus for recording data symbols of the type which are machine readable.

While not necessarily limited thereto, the present invention has application to printing characters with magnetic ink, whereby data can be printed on record forms such as checks or the like which are adapted to be sensed by magnetic pickup devices to control mechanisms for handling the forms.

In banking operations, check forms are now used which carry data printed with a set of stylized symbols commonly known as E-l3B characters. Relatively strict standards of impression quality have been established in an effort to achieve reliability in check processing machines. The nature of the characters present difiiculties in meeting the standards using engraved or embossed type to impact print the characters from a magnetic ink ribbon, especially if the type is flexibly mounted.

Essentially the problem stems from the fact that the 15-1313 characters vary considerably in impression surface area and the surface area within certain characters is nonsymmetrically distributed. The major method of adjusting the impact force level in proportion to the surface area of the type becomes unduly complex in high speed impact printers where any of the printing hammers may be required to print any of the E-13B characters. In addition, where a high degree of asymmetry exists in the character, particularly where the type is flexibly mounted, mere change in impact force level results in non-uniform impression density or embossing outside the standards established by the banking industry.

It is therefore an object of the present invention to provide an improved impact printer apparatus in which the above-mentioned difiiculties, are resolved.

It is a specific object of the prcsentinvention to provide an improved type mechanism for use in impact printers, which accomplishes a more uniform impression density and minimizes embossing in accordance with intra-character variations in character surface area.

It is a further object of the present invention to achieve the above objects in economical manner and without complication in the print mechanism design.

In general, the principle of the present invention whereby the above as well as other objects may be attained, involves distributing the print force applied to the type so that the type element impacts the print medium with an impact force gradient which corresponds to the surface area distribution of the character formed on the type element.

Specifically, the principle of the present invention whereby the above, as well as other objects may be attained, involving causing a type element to impact a print medium in such a manner that the region of the type character thereon having a greater surface area impacts with a heavier force than a region with a lesser surface area. Thus in effect, the type face impacts the print medium with a force gradient which corresponds with the surface area distribution of the character thereon. This is accomplished in accordance with the practice of this invention by causing the portion of the type element having the greater area of type surface to strike ahead of the lesser area portion.

In a preferred embodiment of the present invention, the above principles are incorporated in a high speed printer comprising a horizontal type bar which reciprocates across a print medium. The type bar comprises plural fiat spring type elements having one end fixed to a carrier bar with the free or distal end of the spring element bearing on a type character which is to be impacted against a print medium. A plurality of hammers arranged in a row parallel with the type bar strike the rear surfaces of the type elements in the regions behind the engraved characters, thereby deflecting the free ends of the spring type elements and impacting the embossed characters against the ribbon and the print medium, which is backed up by a platen.

To correct for the unbalanced or uneven embossing caused by the asymmetric area distribution of a character on the otherwise symmetrical spring type element, the rear surface of the print type element immediately behind the embossed character, which is adapted to be impacted by a print hammer for the purpose of driving the raised type character against the print medium is inclined relative to the striking surface of the hammer so as to leave a high portion of the type element behind the maximum area portion of the character. In the case of the E-13B numeral 7, this means that the rear surface on the spring element is inclined from back to front in a right to left direction to compensate for the area portion of the vertical leg of the numeral 7 at the right side of the type element, while it is also inclined from top to bottom in a direction from back to front, to compensate for the unbalanced upper bar area portion of the El3B numeral 7, thus giving a compound rear surface to the spring type element. This surface when struck by a print hammer having a face parallel to the surface of the type character, causes the spring character bearing element to deflect with a compound motion so that the vertical leg and the upper leg portion strike the print medium ahead of and with greater force than the rest of the type.

It is understood that the same effect could be achieved by applying a similar incline to the face of the type, but the complications arising from changes in character line width due to the slopes of the sides of the characters make this a more diificult approach.

The foregoing and other objects, features and advantages cf the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is an isometric or perspective view in part of a bar printer showing the general arrangement of the type elements, print medium, platen and type ribbon;

FIG. 2 is an enlarged side elevation of the platen, print medium, ribbon, type element, type hammer and operating mechanisms thereof used in the printer of FIG. 1;

FIGS. 3a, 3b and 3c are fragmentary top plan views to enlarged scale of a type element, a portion of a hammer, a print medium and a portion of the platen to an exaggerated scale showing the action of the print element during transit after having been struck by the hammer up till the time it impacts the print medium;

FIGS. 4a, 4b, 5a, 5b, and 6a, 6b are plan views of type elements with a portion of a type hammer, together with corresponding front elevation showing different arrangements of lateral incline or taper;

FIGS. 7, 8 and 9 are left-hand, rear and right-hand views of a portion of a type element showing the arrangement of the tapers in two directions;

FIG. is an enlarged isometric partial view of the top portion of a type element; and

FIGS. 11a, 11b and 110 are enlarged side elevations of a print element showing the element in the free position, an intermediate position, and the impacting position, drawn to an exaggerated scale to illustrate the fiexing action of the spring finger.

Referring particularly to FIG. 1, the reference numeral 10 denotes generally a portion of a printer mechanism which includes a print roll 12 mounted on a shaft 14, and having platen inserts 16 for backing up a print medium 18 associated with a vertically movable ribbon 20, both the print medium and the ribbon being advanced in any suitable manner. A plurality of uniformly spaced print hammers 22 is arranged in a linear array along a print line, one hammer being located at each of a plurality of print positions. While various forms of hammers may be used and various assemblies and operators employed to obtain the operation of the hammers at the various print positions, the preferred print hammer mechanism takes the form described in United States patent application of Roland D. Nelson and Donald K. Rex, Ser. No. 113,201, filed May 29, 1961. As shown briefly in FIGS. 1 and 2, in the hammer apparatus of the aforesaid application, each hammer comprises a body portion 24, having a slot 26, whereby the hammers are pivotally mounted on a common stationary support rod 28. The hammer mechanisms 22 further include a striking arm 30 extending outward-1y from the central body portion at the top and a firing arm or tail portion 32 extending below the body portion 24 and slightly to the rear thereof.

Referring further to FIGS. 1 and 2, each hammer 22 in the preferred version of a hammer operator mechanism is provided with an individual holding magnet 33 haying suitable energizing means such as a .winding 35. A return spring 37 is attached at one end to a stationary support 38 and has its free end in biasing contact with the body portion 22 at the edge surface above the pivot rod 28;

The hammer firing mechanism of the aforesaid application includes a cantilever leaf spring 40 for each hamrner, each spring being mounted on a bail 42 which is pivotally suspended from a shaft 43 on one or more spaced arms 45. Each spring drive 40 is made up of a number of leaves 40a, 48b, 40c and 40d of progressively decreasing lengths. The drive mechanism includes a spring reset assembly made up of a spring stop bail 46 pivotally mounted on shaft 43 by means of an arm 48. Each hammer firing mechanism is operated by one or more pairs of cams 49 and 50 which are keyed in an appropriate manner to a rotatable shaft 52. Cam follower 53 is carried .by arms 45 in position to bear against the cam 49, while c-a'm follower 55 is carried by arm 48 to bear against the cam 50. Cam followers 53 and 55 are kept in contact with their respective cams through the actionof springs 57. While FIG. 2 shows a hammer firing mechanism for single hammer 22, it is of course understood that the same firing mechanism wouid be supplied for each of the hammers 22 of the printer apparatus of FIG. 1. For this purpose, the various shafts 43 and 52 may be mounted on a common support frame which supports the hammer mechanisms 22, the platen and the return spring 37 of the printer apparatus of FIG. 1.

Positioned between the print hammers 22 and the type ribbon 20 is a type carrier device comprising a plurality of spring leaf type elements 69 removably mounted on a horizontal reciprocating type element support tube 61. Each of the type elements 60 includes a base mounting portion 62 disposed to be inserted in the support tube 61 and held by spring 62b and a plurality of coplanar fiat integral spring finger extensions 63 having type characters (not shown) formed on front faces at the distal or free ends thereof.

In the line printer apparatus of FIG. 1,. each type hearing finger 63 of 'type element 60 has a type character thereon comprising a different one of the numerals 0-9 and one or more special characters used in the E-13B printing. In practice, El3l3 segments are used every fourth segments along a tube containing twelve segments. However, the fourteen character E-l3B segments may be inserted in each of nine positions in a fourteen character type bar. In accordance with this invention as therein described, a complete arrangement of E-13B characters is provided for printing by assembling plural type elements 60, Le, segments, in a releasable manner by spring 62b on support tube 61 so that each type segment 60 is individually removable and replaceable in the assembly. To print the various characters required in the E-l3B category on the paper 18, type elements 60 are moved horizontally past the array of hammers 22 and the various hammers are selectively operated to strike appropriate type characters at predetermined positions under the control of means which mightinclude memory devices or the like (not shown).

The operation of the firing mechanism for causing the hammers 22 to strike the type bearing fingers 63 of type element 60 is described briefly as follows: Bail 46 positions spring 46 so that they may slide up along side of tail 32. Then bail 46 retracts to positions shown. Bail 42 does two things. It causes vertical displacement of the type of spring 40 and it loads the spring. Shaft 52 stops in position ready for firing when follower 53 is on a high dwell and follower 55 is on a low dwell. The rotation of shaft 52 clockwise first causes cams 49 and 50 to assume a position which causes follower 55 to drop arm 48 causing bail 46 to assume theretracted position shown. Then arm 48 raises and moves bail 46 to the right. As shaft 52 continues to rotate, cam follower 53 raises arm 45 and bail 42 upwardly, so that spring 46a moves vertically and engages the right side of extension 32 of hammer 22. With winding 35 holding magnet 33 energized, hammer 22 is subjected to a clockwise force caused by the deflection of spring 40a as it is brought to bear on extension 32 through the rotation of the cams by shaft 52. When a type finger 63 has been positioned at the appropriate position in front of a hammer 22, the current in coil 35 may be switched off and the control magnet .33 releases hammer 22. Due to the force applied to the extension 32 by spring 40a, hammer 22 pivots about shaft 28. As the hammer pivots, the tip of the spring 40a slides off the lower tip of the firing arm 32 as shown in FIG. 2 and comes to rest against the spring stop bail 46. The acceleration given to the hammer 22 causes it to continue in its clockwise movement until it strikes the type finger 63 and forces the type against the ink ribbon 20, the print medium 18 and the platen 16. Hammer 22 then rebounds away from platen 16 in a counterclockwise direction toward the holding magnet 33 The hammer return spring 37 hearing against the upwardly extending flange of body portion 24 acts to hold the hammer after rebound in cooperation with the magnet 33. Further details of operation of the hammer firing mechanism as well as information on the repetitive selective firing of the hammers 22 as various type fingers 63 are moved into position may be more fully understood by referring to the description in the aforesaid application of Roland D. Nelson and Donald K. Rex.

The horizontal motion of the type carrier which brings the various type fingers 63 into the various print positions, may be provided by a rack and pinion gear arrangement which includes a pinion gear 64 connected in a suitable manner to any well known reversible drive member (not shown) and a rack gear 65 which is attached to the underside proximate one end of the support tube 61;

A flag member 66 attched to the upper side of tube support member 61 moves through a detector means 67 which may comprise suitable photoelectric sensing devices or the like, which through suitable control means connected to the pinion gear drive, limits the stroke of the support tube 61 and reverses its drive current as necessary.

Printing by operation of the hammers 22 to strike the type fingers 63 of type element 60 may be performed at rest or on-the-fiy. In the former case, type carriers 60 move into position so that each type finger is aligned with a different hammer 22 and then stopped. Hammer 22 is fired, then the type carrier moves the type elements 60 to the next horizontal position, aligning each of the type fingers 63 at the next adjacent hammer position. The process is repeated for the full length of the print line. When printing occurs on-the-fly, the tube support member 61 is moved without intermediate interruption across the entire length of the stroke parallel to the print medium 18. In either case, when hammers 22 strike the type fingers 63, the same bending action of the fingers 63 causes them to be displaced from the plane of the type elements 60. In accomplishing such deflection, the hammer means 22 enters the confines of the type element 60. It will be readily apparent that to accomplish the successive step-like movement or the continuous sweeping movement of the type elements 60 past the hammer mechanisms at high speeds, a failure on the part of the hammer mechanism 22 to be retracted might cause some difficulty which would tend to damage the print mechanism. In addition, it will be readily appreciated that extensive oper ation of the printer apparatus in the manner just described causes wear and other mechanical problems which may require the replacement of the type elements 60 from time to time. In the embodiment shown in FIG. 1, each of the type elements or segments 60 is a flat spring leaf member having a common base portion 62 from which a plurality of integral deflectable type fingers 63 extend in a common plane with each other and the base portion 62. The base portion 62 comprises a single mounting extension insertable into a longitudinal slot in the support tube 61. The mounting extension is provided with a central dovetail shaped slot 62:! disposed to be engaged by cooperating fingers of spring clip 62]; mounted in the support tube. The individual type elements 60 may thus be snapped into place in their respective slots in the support tube 61 and likewise may be readily removed for repair or maintenance purposes or for setting up a different configuration of type.

Referring to FIGS. 3a through 30, it will be seen that in FIG. 3a the striking arm 30 of a print hammer 22 is making its initial contact with the rear side of a spring leaf type element 63 which has on its front face an embossed type character 63a. As shown, the rear face of the type elements 63 is beveled or inclined, the portion to the left being removed to provide a rear surface inclined from the rear right toward the front left, so that the striking arm 30 engages the righthand portion of the type element 63 initially. Referring to FIG. 3b, the striking arm 30 is shown in an intermediate position carrying the upper end of the type element 63 with it as it moves toward the print medium. In this intermediate position the type element 63 is shown as twisted so that the rear inclined face is now parallel with the front face of the striking arm 30, and the forward surface of the type character 63a is now inclined backwardly from right to left so that the right-hand portion is ahead of the left-hand side.

Referring to FIG. 30, it will be seen that the character 63a strikes the print medium in the position forcing the ribbon 20 and print medium 18 against the platen 16 so that a greater striking force is exerted at the righthand edge of the character to compensate for the greater resistance encountered thereby, t-hus balancing the imprint made by the type character on the print medium 18. As shown by the dotted line 63b in FIG. 3a, the rear surface of the type element 16 shown is provided with a evel or incline in the vertical direction as well as one from side to side. This is representative of the E13B numeral 7 as shown in FIGS. 6a and 6b where the vertical section of the numeral 7 .is seen to be on the righthand side of the type element, and presents a major portion of the character print area; and the vertical bar of the numeral 7 presents another major area portion of the type element at the top. The first quadrant thus contains the maximum character area, and lesser portions occur in the second and fourth quadrants. By inclining the rear surface of the type element 63 forward from right to left, and forward from top to bottom vertically, the asymmetric arrangement of the character print area may be compensated for to provide a uniform imprint on the print medium.

Referring to FIGS. 52: and 5b, there is shown a representation of the E-13B numeral 8 which is more or less symmetrical, and in which case the rear face of the type element 63 is parallel to the front face of the character 63a. However, the vertical distribution is bottom-heavy. Therefore, this character could have a top to bottom incline with the incline running toward the rear as we go from bottom to top. In FIGS. 4a and 4b are shown the plan and elevational views of a type element 63 hearing the E-13B, or special character 88-4 in which the two rectangular portions to the left have equal areas sub stantially larger than that of the rectangular portion to the right. This provides a generally reverse condition from that encountered with the numeral 7 in FIGS. 6a and 6b, thus calling for a single bevel or inclination of the rear surface of the type element 63 in a forward direction from left to right so as to permit the striking member 30 to engage the left-hand edge of the type member 63 first and thus provide the principal driving force behind the maximum character area to compensate for the increases in resistance encountered when the character impacts the print medium, to thereby provide a more uniform impression.

Referring to FIGS. 7, 8 and 9, there are shown lefthand, rear and right-hand elevations of a portion of a type element 63 corresponding to the type element shown in FIGS. 3c23c which carry the E-13B numeral 7 on the face thereof. As shown, it will be seen that the rear face of the print member 63 is inclined to the vertical, material being removed from the lower portion of the rear face immediately behind the character, so that the rear face slopes toward the front from the top downwardly, while at the same time having a transverse bevel or incline so that in FIG. 7 the rear surface is inclined from the surface into the paper toward the right, and in FIG. 8 the dotted line 630 designates the same incline in the lateral direction.

FIG. 10 is an isometric or perspective view of the type element 63 of FIGS. 7, 8 and 9 showing the compound incline of the rear surface engaged by the striking bar 30 in both the vertical and horizontaldirections. An inclination in the order of 15 has been found to be effective both vertically and transversely in the case of the numeral 7, for example.

Referring to FIGS. 11a, 11b and 11c, these three figures may be considered in connection with the corresponding FIGURES 3a, 3b and 30 for showing the reaction of a print element having both vertical and transverse inclination of the rear surface to compensate for an asymmetric type character 63a.

Referring to FIGS. 11a and 3a, it will be seen that in the initial position of the type element 63, the front of spring finger type element 63 is as shown in FIG. 3a parallel to the print medium 18 and in FIG. 11a edgewise or perpendicular to the plane of the paper. It will be noted from the top view in FIG. 3a that the rear surface of the finger 63 immediately behind the character 63a is inclined a forward direction from right to left as is shown by the dotted line 630 in FIG. 11a. In addition, the rear face of the finger 63 is inclined in the vertical direction, the lower end being further forward so that the rear face slopes upwardly toward the end of the finger. This is clearly shown in FIG. 11a in which it may be seen that the rear surface of the finger behind the character is inclined relative to the left-hand side or rear surface of the finger 63 generally. This is shown in FIG. 3a by the dotted line 6312.

When the striking arm 30 of the print hammer engages the rear base of the spring finger 63, since the finger is made of a spring material and is resilient, it will be seen from FIG. 3b that the arm 30 imparts a tWist to the finger 63 so that the face of the character 63a is no longer paraliel to the print medium 18. As shown, the righthand edge of the character moves forward reiative to the left-hand edge as the rear face of the finger 63 aligns itself with the face of the striking arm 36, which is parallel to the print medium 18. Referring to the intermediate FIG. lib, this action is shown by the twist imparted to the finger 63, evidenced by the fact that the rear portion of the finger in this figure, or the left-hand side when viewed from the rear as in FIG. 312, now becomes visible as the near side or right-hand edge moves forward under the influence of the striking arm 36. At the same time, the print arm 30 having engaged the upper surface of the rear of the finger 63, deflects it, moving it forward so that the rear surface of the finger at the end is now substantially parallel to the print medium or in this case, tangent to the adjacent portion to the flexed finger 63. This places the front surface of the character with the top portion ahead of the lower portion and the near side in FIG. 11b ahead of the far side looking into the paper.

Referring to FIGS. 3c and 110, it will be seen that the character 63a is impacted against the print medium With the right-hand edge leading, as shown in FIG. 3c, and as this is the location of principal character area, it meets with the most resistance in imprinting on the print medium, so that the face of the character 63a tends to return to a position more nearly parallel to the print medium during the actual typing operation. Referring to FIG. 11c it will be seen that the rear surface of the finger 63 is now inclined forwardly at the top, relative to the adjacent portion of the finger, so that the top edge which in this instance carries a horizontal bar on the FIGURE 7, is driven against the print medium first and with a greater force than the lower portion, and this compensates for the greater resistance that it meets in making the impression on the print medium. Thus it results in a uniform impression from top to bottom and from side to side.

From the above description and accompanying drawings it will be seen that by practicing the invention, more uniform print results are obtained. Embossing, which is critical in connection with the -E-13B printing, where no more than .001" embossing is permitted, may be readily controlled. A modification of the impact surface at the rear of the type character tends to distribute the pressure more uniformly, since the flexible type finger tends to conform to the surface of the hammer striking it. In some characters there is a greater area at the top than at the bottom; in others, there is a greater area to the right or to the left. To compensate for this asymmetric area distribution of characters, the back of the finger is inclined so as to be depressed by grinding or otherwise removing material from the back of the finger in the region of least character area. While we have shown the finger modification as applied to the back of a finger, it

i may also be applied to the type face, in which case the face of the type is modified so that the portion of greater area protrudes slightly further toward the print medium than that of the lesser area.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein Without departing from the spirit and scope of the invention.

8 What is claimed is: 1. In a printer apparatus, the combination comprising a platen, a type element movably :mounted proximate said platen, said type element having a front surface for impacting a record medium against said platen,

said type element having on said front of said type element a raised character the surface of which lies in a plane generally parallel with said platen surface, said character surface having an asymmetrical distribution on said front surface of said type element,

said type element having a rear surface adapted to be struck for moving said type element to impact said platen,

said rear surface being inclined relative to the plane of said character surface,

said inclination being related to the surface distribution of said character,

and means for impacing said rear surface of said type element,

said impacting means having an impacting surface parallel with the plane of said character surface.

2. In a printer apparatus, the combination in accordance with claim 1 in which the inclination of said rear surface progresses from a [minimum in the region behind the maximum character surface to a maximum in the region behind the minimum character surface.

3. In a printer apparatus, the combination in accordance with claim 1 in which said 'rear surface of said type element has a compound inclination.

4. In a printer apparatus, the combination in accordance with claim 3 in which the slope of said compound inclination extends in lateral direction as well as from top to bottom in the regions behind said character.

5. In a printer apparatus, the combination in accordance with claim 4 in which said character surface distribution is greater in the first quadrant and lesser in the second and fourth quadrants and said compound inclination increases from a maximum behind said first quadrant to minimums behind said second and fourth quadrants.

6. In a printer apparatus, the combination in accordance with claim I in which the type element is mounted on a resilient support which permits additional movement of the type element as a result of the inclined rear surface in addition to the movement in the direction of the platen.

7. In a printer apparatus, the combination in accordance with claim 1 in which the type element is mounted at the free end of a fiat cantilever spring finger which permits rotational movement of the type element as well as translation in the direction of the platen.

8. In a printer apparatus, the combination in accordance with claim 3 in which the type element is mounted on the distal end of an elongated flat spring finger.

9. In a printer apparatus, the combination in accordance with claim 3 in which the type element is mounted on the distal end of a fiat cantilever spring finger which is parallel to the axis of the platen.

10. In a printer apparatus, the combination comprising a platen having a surface engageable by a type element,

a type element movable to engage said platen,

said type element having a raised character on one side facing said platen,

said raised character having an impression surface engageable with said platen to cause impressions to be made,

said impression surface being asymmetrically distributed over said side of said type element,

said'type element having a second surface behind said raised character,

and a hammer for driving said type element in the direction of said platen, a

said hammer having a surface engageable with said second surface of said type element, one of the engaging surfaces of said platen, said type element, and said hammer element being inclined at an angle relative to the direction of motion of said type element and to said other engaging surfaces, said inclination causing said impression surface of said type element to engage said platen with a force distribution corresponding with the distribution of said impression surface of said raised character. 11. In a printer apparatus, the combination in accordance with claim 10 in which said one inclined surface is said second surface on said type element, said inclined surface causing said type element to be turned at an angle relative to the direction of motion whereby said character impression surface engages said platen with a force distribution corresponding with the distribution of said impression surface on said type element. 12. In a printer apparatus, the combination in accordance with claim 10 in which said one inclined surface is said second surface on said type element, said inclined surface causing said type element to be turned by said hammer to cause the region of maximum character surface area to engage said platen with greater force than said region of minimum surface area. 13. In a printer apparatus, the combination in accordance with claim 11 in which said type element is a spring leaf type element having one end fixed to a type carrier and the distal end displaceable on contact by said print hammer toward said platen,

said raised character being on one side of said spring leaf proximate said distal end thereof,

and said second surface behind said raised character is inclined to effect a twisting and bending of said spring leaf at said distal end upon displacement by said hammer in accordance with the asymmetrical distribution of said impression surface.

14. In a printer apparatus, the combination in accordance with claim 11 in which said type element is a spring leaf type element having one end fixed to a type carrier and the distal end displaceable by said print hammer toward said platen,

said raised character being on one side of said spring leaf proximate said distal end thereof,

and said second surface behind said raised character is inclined for effecting a twisting of said spring leaf at said distal end upon displacement by said hammer in accordance with the asymmetrical distribution of said impression surface.

References Cited by the Examiner UNITED STATES PATENTS 2,935,935 5/1960 Preston et al. 10193 2,936,704 5/1960 Hense 10193 3,144,821 8/1964 Drejza 10l93 3,175,486 3/1965 Athens et al 10193 3,209,682 10/1965 Cooper 101-109 3,241,480 1/1966 Cunningham 10193 OTHER REFERENCES IBM Technical Disclosure Bull. vol. 4, No. 6, November 1961, page 9. Copy 101-109.

WILLIAM B. PENN, Primary Examiner. 

1. IN A PRINTER APPARATUS, THE COMBINATION COMPRISING A PLATEN, A TYPE ELEMENT MOVABLY MOUNTED PROXIMATE SAID PLATEN, SAID TYPE ELEMENT HAVING A FRONT SURFACE FOR IMPACTING A RECORD MEDIUM AGAINST SAID PLATEN, SAID TYPE ELEMENT HAVING ON SAID FRONT OF SAID TYPE ELEMENT A RAISED CHARACTER THE SURFACE OF WHICH LIES IN A PLANE GENERALLY PARALLEL WITH SAID PLATEN SURFACE, SAID CHARACTER SURFACE HAVING AN ASYMMETRICAL DISTRIBUTION ON SAID FRONT SURFACE OF SAID TYPE ELEMENT, SAID TYPE ELEMENT HAVING A REAR SURFACE ADAPTED TO BE STRUCK FOR MOVING SAID TYPE ELEMENT TO IMPACT SAID PLATEN, SAID REAR SURFACE BEING INCLINED RELATIVE TO THE PLANE OF SAID CHARACTER SURFACE, SAID INCLINATION BEING RELATED TO THE SURFACE DISTRIBUTION OF SAID CHARACTER, AND MEANS FOR IMPACING SAID REAR SURFACE OF SAID TYPE ELEMENT, SAID IMPACTING MEANS HAVING AN IMPACTING SURFACE PARALLEL WITH THE PLANE OF SAID CHARACTER SURFACE. 